120H, 12H, 135H, 140H, 143H, 160H and 163H Motor Graders Hydraulic and Steering System Caterpillar

Low Standby Pressure Adjustment

Note: Before you perform this adjustment, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Illustration 1	g00932010
Side view of combination valve (1) Hydraulic tank return port (2) Steering supply port (3) Combination valve (4) Secondary steering pump port (5) Pressure switch port (6) Supply port for the valve group (7) Supply port for the valve group (8) Steering signal (9) Steering relief valve (10) Implement relief valve (11) Valve group return port (12) Auxiliary return port (13) Pressure test port for the hydraulic and steering pump (14) Control valve signal (15) Pump signal (16) Signal purge valve (17) Signal relief valve

Illustration 2	g00932013
Pressure and flow compensator valve (18) Purge valve for the flow compensator (19) Port (20) Adjustment screw for the flow compensator (margin pressure) (21) Locknuts (22) Adjustment screw for the pressure compensator (pressure cutoff)

Illustration 3	g00932015
Section A-A of pressure and flow compensator valve (18) Purge valve for the flow compensator (19) Port

The combination valve and the pressure and flow compensator valve are accessible from the ground. The valves are located under the cab platform and on the left side of the machine. These components are near the rear cab support.

1. Start the engine.

2. Operate the engine at low idle. Operate the implement controls for three to ten minutes in order to raise the hydraulic oil temperature to normal operating temperature range.

3. Stop the engine.

4. Remove the dust cover from pressure test port (13). Install a 198-4240 Digital Pressure Indicator with a 198-4238 Pressure Sensor onto pressure test port (13) .

5. Start the engine. Operate the engine at high idle. Record the pressure reading from the digital pressure indicator at pressure test port (13). The pressure should read 3310 ± 690 kPa (480 ± 100 psi). If the low pressure standby is too high, refer to the Problem: Low standby pressure is too high within Testing and Adjusting, "Hydraulic and Steering System Troubleshooting".

6. Open purge valve (18) counterclockwise by one turn. A small amount of oil may leak by the purge valve during this procedure.

7. Read the pressure gauge. The correct setting for true low pressure standby is 2100 ± 100 kPa (305 ± 15 psi). This reading is without any load from the implements or any load from the steering on the hydraulic system.

8. If the pressure reading is incorrect, close purge valve (18). Proceed to Section "Adjustment for Flow Compensator (Margin Pressure) ".

Adjustment for Flow Compensator (Margin Pressure)

Note: Before you perform this adjustment, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Illustration 4	g00932013
Pressure and flow compensator valve (18) Purge valve for the flow compensator (19) Port (20) Adjustment screw for the flow compensator (margin pressure) (21) Locknuts (22) Adjustment screw for the pressure compensator (pressure cutoff)

Illustration 5	g00932145
(13) Pressure test port for the hydraulic and steering pump (19) Port

1. Connect the low side of the 1U-5796 Pressure Differential Gauge Group onto port (19). Port (19) receives the resolved signal from the combination valve.

2. Connect the high side of the 1U-5796 Pressure Differential Gauge Group onto pressure test port (13) .

3. Start the engine.

4. Operate the engine at low idle. Operate the implement controls for three to ten minutes in order to raise the hydraulic oil temperature to normal operating temperature range.

5. When you obtain the normal operating temperature for the hydraulic oil, operate the engine at high idle.

6. Operate the circle drive and rotate the blade at full speed. Record the gauge pressure.

7. Stop the engine. The pressure reading should be 2100 ± 100 kPa (305 ± 15 psi).

8. If the pressure reading is incorrect, loosen locknut (21) on adjustment screw (20). Turn the adjustment screw clockwise in order to increase the setting. Turn the adjustment screw counterclockwise in order to decrease the setting.

9. When you tighten locknut (21) hold adjustment screw (20) secure. Repeat Steps 5 through Step 8 until you obtain the correct pressure setting in Step 7.

10. Remove the pressure gauge. Replace the dust caps on pressure test port (13) and port (19) .

Adjustment for Hydraulic System Pressure

Illustration 6	g00932010
Side view of combination valve (1) Hydraulic tank return port (2) Steering supply port (3) Combination valve (4) Secondary steering pump port (5) Pressure switch port (6) Supply port for the valve group (7) Supply port for the valve group (8) Steering signal (9) Steering relief valve (10) Implement relief valve (11) Valve group return port (12) Auxiliary return port (13) Pressure test port for the hydraulic and steering pump (14) Control valve signal (15) Pump signal (16) Signal purge valve (17) Signal relief valve

Note: Before you perform this adjustment, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Note: When you perform this adjustment and there is a loss of oil from spillage, use approved containers to contain the oil. Also, use these approved containers in order to dispose of the oil.

1. Start the engine.

2. Operate the engine at low idle. Operate the implement controls from three minutes to ten minutes in order to raise the hydraulic oil temperature to the normal operating temperature range.

3. Stop the engine. Remove the dust cover from pressure test port (13). Install the 198-4240 Digital Pressure Indicator with a 198-4239 Pressure Sensor onto pressure test port (13) .

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Illustration 7	g00932013
Pressure and flow compensator valve (18) Purge valve for the flow compensator (19) Port (20) Adjustment screw for the flow compensator (margin pressure) (21) Locknuts (22) Adjustment screw for the pressure compensator (pressure cutoff)

4. Start the engine and operate the engine at high idle. When you are checking for the implement cylinder stall pressure, move the wheel lean cylinder to the end of the stroke. Then stall the wheel lean cylinder. The correct pressure reading should be 24132 ± 1034 kPa (3500 ± 150 psi).

5. Stop the engine if the pressure reading is incorrect. Loosen the locknut for signal relief valve (17). Turn the signal relief setscrew clockwise in order to increase maximum pump pressure. Turn the signal relief setscrew counterclockwise in order to decrease maximum pump pressure. One clockwise turn of the setscrew will increase the setting by approximately 4700 kPa (682 psi). One counterclockwise turn of the setscrew will decrease the setting by the same amount. While you tighten the locknut, hold the setscrew firmly. Start the engine and recheck the pressure reading.

6. Stop the engine in order to adjust implement relief valve (12). Remove signal relief valve (17) from the combination valve. Remove the left blade lift relief valve from the left blade lift control valve. Install signal relief valve (17) in the left blade lift control valve. Install the left blade lift relief valve in the combination valve.

7. Loosen locknut (21) and turn adjustment screw (22) clockwise by two complete turns.

8. Start the engine and operate the engine at high idle. Move the wheel lean cylinder to the end of the stroke and stall the cylinder. The pressure gauge should read 27600 ± 400 kPa (3900 ± 60 psi). This is the pressure setting of implement relief valve (10) .

9. If the pressure is incorrect, stop the engine. Loosen the locknut on implement relief valve (10) .

10. Turning the setscrew clockwise will increase the pressure and turning the setscrew counterclockwise will decrease the pressure. While you tighten the locknut, hold the setscrew firmly. Start the engine and operate the engine at high idle. Move the wheel lean cylinder to the maximum stroke and stall. Check the pressure reading.

Note: If you cannot achieve 27600 ± 400 kPa (3900 ± 60 psi), replace the implement relief valve (10) .

11. Stop the engine. Turn adjustment screw (22) counterclockwise by two complete turns.

12. When you adjust adjustment screw (22), start the engine. Operate the engine at high idle. Move the wheel lean cylinder to the end of the stroke and stall the cylinder. The pressure gauge should read 25500 ± 350 (3700 ± 70 psi).

13. If the pressure is incorrect, stop the engine. Loosen locknut (21) on adjustment screw (22) .

14. Turn adjustment screw (22) clockwise in order to increase the pressure. Turn adjustment screw (22) counterclockwise in order to decrease the pressure. While you tighten locknut (21), hold adjustment screw (22) firmly. Start the engine and operate the engine at high idle. Move the wheel lean cylinder to the maximum stroke and stall. Check the pressure reading.

15. After you achieve the correct pressure reading, remove the left blade lift relief valve from the combination valve. Remove signal relief valve (17) from the blade lift control valve. Install signal relief valve (17) into the combination valve. Install the left blade lift relief valve into the blade lift control valve. Tighten relief valves to the specified torque.

16. Repeat Step 4.

17. If the pressure reading is incorrect, repeat Step 5.

18. When the pressure reading is correct, stop the engine. Remove the pressure gauge. Install the dust cover on pressure test port (13) .

Adjustment for Signal Network

Note: Before you perform this adjustment, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Illustration 8	g00932145
(13) Pressure test port for the hydraulic and steering pump (19) Port

Illustration 9	g00932021
(3) Combination valve (23) Left blade lift control valve (24) Control valve for the sideshift (25) Circle drive control valve (26) Blade tip control valve (27) Drain (28) Articulation control valve (29) Centershift control valve (30) Wheel lean control valve (31) Right blade lift control valve (32) Signal check valve (33) Line from the steering metering pump (34) Line from the combination valve (35) Signal resolver (36) Line to the pressure and flow compensator valve (37) Line to the signal purge valve and signal relief valve

Note: The number of control valves in the valve bank may vary with the different equipment that is on the machine.

1. Operate the engine at low idle.

2. Operate the implement controls for three minutes to ten minutes in order to raise the hydraulic oil temperature to the normal operating temperature range.

3. Stop the engine. Remove the dust cover from pressure test port (13). Install the 198-4240 Digital Pressure Indicator with a 198-4238 Pressure Sensor onto pressure test port (13) .

4. Start the engine and operate the engine at high idle. The correct pressure reading should be 3300 ± 689 kPa (480 ± 100 psi).

5. If the pressure that is measured at pressure test port (13) is within the tolerance that is indicated in Step 4, proceed to Step 6. If the pressure reading is not within the tolerance, adjust the low standby pressure. Refer to the procedure that is found in the "Low Standby Pressure Adjustment" section. Then continue with Section "Adjustment for Signal Network ".

6. Stop the engine. In order to obtain pump signal pressure, remove the dust cap from pressure test port (19). Install the 198-4240 Digital Pressure Indicator and the 198-4238 Pressure Sensor onto port (19) of the pressure and the flow compensator valve.

7. Move the control lever for blade tip (26) in order to move the blade tip cylinder to the maximum stroke and stall. Read the pressure gauges. The pressure gauge that is reading the pump signal should increase. The pressure gauge that is reading the pump output should increase.

8. If the pump signal pressure increases and the pump output pressure does not increase, the pressure and flow compensator valve on the hydraulic and steering pump has failed. Stop the engine.

9. Replace the pressure and flow compensator valve.

10. Test signal resolver (35) in the combination valve by following Step 11 and Step 12.

11. Start the engine and operate the engine at low idle.

12. When the implement ceases to operate and the steering is not being operated, signal resolver (35) in the combination valve has failed.

13. Stop the engine. Remove the pressure gauge from pressure test port (13). Replace the dust cover.

14. In order to check for a faulty signal check ball in the implement control valves, follow Steps 15 through Step 20. In order to check for a missing signal check ball in the implement control valves, follow Steps 15 through Step 20.

15. Start the engine and operate the engine at low idle. Check the implement cycle times.

16. If the cycle time for each of the implements is longer than the specifications that are allowed except for one implement, the following information is true. The signal check ball in that implement control valve is faulty or the signal check ball in that implement control valve is missing.

17. The signal from the right valve bank can be isolated from the signal from the left valve bank at the combination valve. This will pinpoint the problem with the signal to the right valve bank or to the left valve bank.

18. If a blade lift cylinder drifts during the operation of another implement that is in the same valve bank, the signal check ball in the blade lift cylinder is faulty. A missing signal check ball in any implement valves or a faulty signal check ball in any implement valves may cause any one of the implements to be inoperative in that valve bank. The implement that is working will be the implement valve that is missing a signal check ball or the implement valve that has a faulty signal check ball in that implement valve.

19. Operate the circle drive. If a low flow circuit fails to operate during operation of the engine at low idle, refer to Testing and Adjusting, "Hydraulic and Steering System Troubleshooting".

20. Stop the engine.